Revert "run response header save on background thread during cache item migration"
Revert "run response header save on background thread during cache item migration"

This reverts commit 378c1fbeb4a7532f2f7813b93ef04b232f2f139c.

wikimedia/wikipedia-ios,wikimedia/wikipedia-ios,wikimedia/wikipedia-ios,wikimedia/wikipedia-ios,wikimedia/wikipedia-ios,wikimedia/wikipedia-ios,wikimedia/wikipedia-ios